The present invention relates to improvements to guarded razor blades for shaving. For as long as a man has attempted the removal of hair from the body, energy has been directed to ameliorating the effects of the sharpened cutting edge on the skin of the user. Despite all efforts, occasional skin irritation and blood-letting still occur during the shaving process.
This invention relates more particularly to razor blades having guard elements deposited thereon in retaining seats formed in the edge and flanking sides of the blade.
Numerous methods have been devised to minimize the nicking or cutting of the skin which may occur during shaving, a large portion directed to improved forms of edge guards. A patent to Dickinson, U.S. Pat. No. 1,035,548, issued Aug. 13, 1912, discloses a straight razor having a long blade on which is spirally wound a wire or thread to form a guard. Another form of guard is disclosed by Ferrara in U.S. Pat. No. 3,263,330 issued Aug. 2, 1966, wherein the razor blade cutting edge is encapsulated in a folded sheet of metal having a row of holes through which the hairs but not the skin pass for cutting.
A more recent development is disclosed in U.S. Pat. No. 3,505,734 issued to Iten on Apr. 14, 1970, for a cutting blade with self-contained guard. In this patent, a razor blade with a self-contained guard in the form of a wire is described. The wire or thread of selected diameter is wound about the body of the blade encompassing its ultimate edge. The spacing or pitch between successive turns of the wire is controlled relative to its diameter to provide protection to the skin of the user and diminished probability of cutting or nicking. The selected critical thread diameter and spacing between successive thread portions at the cutting edge of the blade may be drawn across the skin without coming in contact therewith. Some positional stability is given to the wound wire guard elements by spot-welding them to the blade at a location back from its edge and by passing the wire through notches in the blade edge.
Another arrangement similar to that of Iten is disclosed in U.S. Pat. No. 3,750,285 to Michelson issued on Aug. 7, 1973. There the razor blade has a guarded cutting edge comprising a multiplicity of relatively short and thin guard members bent into relatively V-shaped form and secured to the blade edge by permanent attachment of the respective ends of each guard member to the razor blade base structure at points relatively close to the blade cutting edge. Those guard elements as well may be seated in notches formed in the blade edge or, if relatively softer than the blade edge, may have the blade edge embedded therein.
While the self-contained guards of Iten and Michelson may be successful in insulating the skin from the ultimate cutting edge of the razor blade, they do introduce numerous and severe problems into the manufacturing of razor blades incorporating its principal features. The thread or threads must be of flexible material having precise dimensional conformity. It must also be sufficiently flexible for winding about the body of the blade or at least over the blade edge and yet strong enough to withstand severing as it passes over and comes into contact with the blade edge. Moreover, once the wire is placed on the blade, it must be adhesively or otherwise locked into position to prevent interference with shaving and to maintain its advantageous characteristics. With regard to this latter fact, it must be kept in mind that as the wire comes into contact with the ultimate edge of the blade, the edge being 300 to 500 Angstroms in radius, it necessarily damages the blade edge making such contact portion substantially incapable of providing comfortable shaving characteristics. Such method of applying guard elements to the blade edge also inherently increases blade damage, resulting in a less efficient manufacturing operation.
More recently, techniques have been disclosed in U.S. patent applications No. 645,055 filed Dec. 29, 1975, by Beddall for Printed Blade Shield, and No. 911,026 filed May 31, 1978, by Auton for Blade Shields and being a continuation of Ser. No. 778,755 filed Mar. 17, 1977, now abandoned all being assigned to the same assignee as the present invention, for placing guard or shielding elements on a blade edge without many of the shortcomings of the aforementioned prior art techniques. Specifically, epoxy resins may be placed on the edge and flanking facets of a blade using ink jet printing techniques or, alternatively, the guard elements may be deposited by sputtering or ion plating. These techniques overcome some of the objections of the aforementioned prior art techniques. However, the guard elements so deposited may be subject to dislodgement from the blade in response to normal shaving forces and/or abuse.
It is an object of the preferred form of the invention to provide an improved method for applying structural elements to a cutting or razor blade. It is another object of the present invention to provide a razor blade product having structural elements thereon. Another object of the present invention is to provide a razor blade having a deposited guard formed thereon. Yet another object of the present invention is to provide for the placement of guard elements on a razor blade in a manner enhancing their retention on the blade.